Information terminal devices that are used in aircraft, trains, automobiles, and other such moving vehicles need to have a film affixed to a monitor surface in order to prevent the shattering of glass or other materials used in the monitor, to ensure the safety of passengers in the event of a collision. This anti-shatter film has been made of a transparent material that has an even thickness and transmits visible light, so as not to affect input to a touch panel or the visibility of the display panel that lies underneath this. However, the film may be worn off or intentionally peeled off, or a worker may forget to affix it at the manufacturing stage of the information terminal device, so particularly with aircraft, the crew would conduct an inspection, but it took time to confirm whether the film was really there because it was made of a transparent material.
Japanese Laid-Open Patent Application 2003-90987, for example, discusses a way to easily detect that a film made of a transparent material has been peeled off. What Patent Literature 1 discloses allows the user to use a recognition mark attached to the film to check for peeling of a protective film that is supposed to be removed in the manufacturing process. This recognition mark can be checked by eye or with an image processing device to prevent the film from being accidentally applied twice or prevent part of the film from remaining after peeling.